(A) Kaplan-Meier survival curve of Hrb+/+ and Hrb–/– cohorts monitored over a period of 90 weeks. Hrb+/– mice on the background of MMTV-Cre/CBPflox/flox were intercrossed to generate Hrb+/+ and Hrb–/– mice with conditional loss of CBP. Mice were sacrificed once moribund and confirmed via dissection for the occurrence of T cell lymphoma (n = 19 for each cohort; P = 0.0396, log-rank Mantel-Cox test). (B) Western blot of lysates prepared from Hrb+/+ CBP-null tumors (n = 7) and Hrb–/– CBP-null tumors (n = 2). Membrane was blotted for Notch1 protein (clone mN1a), Hrb (clone H-300), and GAPDH (loading control). (C) Western blot of lysates prepared from CBP-null tumors (n = 3) and control thymocytes (n = 2). Membrane was blotted for activated Notch (VAL1744 Ab), Hrb (clone H-300), and actin (loading control). Asterisks indicate nonspecific bands.